Granulocyte antigens play an important role in cell function including adhesion, cell activation, and binding of immunoglobulins. The purpose of these studies is to better define the molecular basis of variations in neutrophil antigens and their role in neutrophil function. Neutrophil-specific antigen HNA-2a (NB1) has been localized to NB1 glycoprotein (gp) which is expressed on subpopulations of neutrophils. The gene encoding the NB1 gp was recently sequenced and called NB1. Another group described a gene called PRV-1 that is highly homologous to NB1. We found that NB1 and PRV-1 are alleles of the same gene, CD177, and showed that this gene is located on chromosome 19q13.31. In addition, we found that a pseudo gene homologous to exons 4 through 9 of CD177 was located adjacent to CD177 on chromosome 19q13.31. We found that the most common polymorphisms of CD177 was a G to C change at bp42. Studies are underway to identify the most common CD177 haplotypes and correlate haplotypes with HNA-1a antigen expression. CD177 is over expressed in neutrophils from patients with polycythemia vera. Future studies will compare HNA-1a, NB1 gp expression, and CD177 haplotypes among healthy subjects and patients with polycythemia vera.